Answer for BIR CoW 17 Feb 2019
LIVER FAT QUANTIFIFICATION MILD HEPATIC STEATOSIS
Findings
The study is the Liver fat Quantification with estimation of Proton Fat Fraction . Proton fat fraction is relatively high (13.5%), reflecting Mild Hepatic Steatosis
Discussion
Non invasive estimation of liver fat can be done by CT or MRI. The LIVER ATTENUATION INDEX is the difference between mean hepatic attenuation and mean splenic attenuation (i.e. average density of liver − average density of spleen on non-contrast CT scan). Liver attenuation is calculated by placing the circular region of interest (ROI) of at least 1 cm² area at multiple places in the liver, covering all the hepatic segments. Care should be taken to avoid inclusion of macroscopic vessels and areas close to fissures during attenuation measurements. Splenic attenuation is measured by placing ROI at its upper, mid, and lower poles Average attenuation of liver parenchyma on non-contrast CT images varies between 50 and 65 HU and is generally 8-10 HU greater than that of spleen. LAI > 5 HU correctly predicted the absence of significant macrovesicular steatosis (Limanond et al. ). LAI values of -10 to 5 HU were suggestive of mild to moderate steatosis (6-30%). while LAI values of less than -10 HU were suggestive of moderate to severe hepatic steatosis (i.e. ≥30% fat) with a specificity of 100%. However MRI based methods like signal /proton fat fraction or MR Spectroscopy are [prefered due to lack of radiation and corrrelating well with histology Proton fat fraction is a useful biomarker for the assessment of NAFLD (Non alcoholic fatty liver disease). Proton fat fraction avoids T1 bias as well as susceptibility artefacts and correlates well with histology. The MRI sensitivities and specificities in detecting histologic steatosis ≥ 5% were 76.7%-90.0% and 87.1%-91%, respectively, and the corresponding MRS performances were 80.0%-91.0% and 80.2%-87.0%, respectively. various studies have graded Liver steatosis based on Proton fat fraction . Permutt et al. based grading values : Grade 1: 8.9% Grade 2: 16.3% Grade 3: 25% Tang et al based grading values: Grade 1: 6.4% Grade 2: 17.4% Grade 3: 22.1% In contrast to single voxel MR Spectroscopy method to assess hepatic steatosis, which collects data from a small portion of the liver (within a voxel ≤ 3 cm × 3 cm × 3 cm), which may be subject to sampling error, MRI is widely available, easily applicable, and can evaluate the entire liver within a short breath-hold.
Ref: 1.Radiologic evaluation of nonalcoholic fatty liver disease World J Gastroenterol 2014 June 21; 20(23): 7392-7402 2.MRI and MRE for non-invasive quantitative assessment of hepatic steatosis and fibrosis in NAFLD and NASH: Clinical trials to clinical practice Journal of Hepatology 2016 vol. 65 j 1006–1016
Findings
The study is the Liver fat Quantification with estimation of Proton Fat Fraction . Proton fat fraction is relatively high (13.5%), reflecting Mild Hepatic Steatosis
Discussion
Non invasive estimation of liver fat can be done by CT or MRI. The LIVER ATTENUATION INDEX is the difference between mean hepatic attenuation and mean splenic attenuation (i.e. average density of liver − average density of spleen on non-contrast CT scan). Liver attenuation is calculated by placing the circular region of interest (ROI) of at least 1 cm² area at multiple places in the liver, covering all the hepatic segments. Care should be taken to avoid inclusion of macroscopic vessels and areas close to fissures during attenuation measurements. Splenic attenuation is measured by placing ROI at its upper, mid, and lower poles Average attenuation of liver parenchyma on non-contrast CT images varies between 50 and 65 HU and is generally 8-10 HU greater than that of spleen. LAI > 5 HU correctly predicted the absence of significant macrovesicular steatosis (Limanond et al. ). LAI values of -10 to 5 HU were suggestive of mild to moderate steatosis (6-30%). while LAI values of less than -10 HU were suggestive of moderate to severe hepatic steatosis (i.e. ≥30% fat) with a specificity of 100%. However MRI based methods like signal /proton fat fraction or MR Spectroscopy are [prefered due to lack of radiation and corrrelating well with histology Proton fat fraction is a useful biomarker for the assessment of NAFLD (Non alcoholic fatty liver disease). Proton fat fraction avoids T1 bias as well as susceptibility artefacts and correlates well with histology. The MRI sensitivities and specificities in detecting histologic steatosis ≥ 5% were 76.7%-90.0% and 87.1%-91%, respectively, and the corresponding MRS performances were 80.0%-91.0% and 80.2%-87.0%, respectively. various studies have graded Liver steatosis based on Proton fat fraction . Permutt et al. based grading values : Grade 1: 8.9% Grade 2: 16.3% Grade 3: 25% Tang et al based grading values: Grade 1: 6.4% Grade 2: 17.4% Grade 3: 22.1% In contrast to single voxel MR Spectroscopy method to assess hepatic steatosis, which collects data from a small portion of the liver (within a voxel ≤ 3 cm × 3 cm × 3 cm), which may be subject to sampling error, MRI is widely available, easily applicable, and can evaluate the entire liver within a short breath-hold.
Ref: 1.Radiologic evaluation of nonalcoholic fatty liver disease World J Gastroenterol 2014 June 21; 20(23): 7392-7402 2.MRI and MRE for non-invasive quantitative assessment of hepatic steatosis and fibrosis in NAFLD and NASH: Clinical trials to clinical practice Journal of Hepatology 2016 vol. 65 j 1006–1016
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!